The present invention generally relates to an apparatus for therapeutically treating and/or analyzing conditions of the inner ear, and more particularly to a multi-functional medical apparatus for use in connection with the middle and inner ear in which the apparatus is capable of (1) delivering therapeutic agents including various medicines in fluid form to internal ear (e.g. inner ear) structures; (2) extracting, withdrawing, or exchanging fluid materials from the inner ear; (3) transferring fluid materials into and out of the inner ear via the round window membrane so that items (1) and (2) can be accomplished; (4) enabling middle and inner ear structures to be electrophysiologically monitored using electrocochleography ("ECoG") procedures; and (5) altering the permeability of the round window membrane in the ear for a variety of therapeutic purposes.
In order to treat ear disorders, it may often be necessary to deliver therapeutic agents to various ear tissues in a controlled, safe, and efficient manner. For example, a variety of structures have been developed which are capable of delivering/administering therapeutic agents into the external auditory canal of the outer ear. U.S. Pat. No. 4,034,759 to Haerr discloses a hollow, cylindrical tube manufactured of sponge material (e.g. dehydrated cellulose) which is inserted into the external auditory canal of a patient. When liquid medicines are placed in contact with the tube, it correspondingly expands against the walls of the auditory canal. As a result, accidental removal of the tube is prevented. Furthermore, medicine materials absorbed by the tube are maintained in contact with the walls of the external auditory canal for treatment purposes. Other absorbent devices designed for treatment of the external auditory canal and related tissue structures are disclosed in U.S. Pat. No. 3,528,419 to Joechle, U.S. Pat. No. 4,159,719 to Haerr, and U.S. Pat. No. 2,642,065 to Negri. The Negri patent specifically discloses a medicine delivery device with an internally-mounted, frangible medicine container which, when broken, releases liquid medicines into an absorbent member.
However, the delivery of therapeutic agents in a controlled and effective manner is considerably more difficult with respect to tissue structures of the inner ear (e.g. those portions of the ear surrounded by the otic capsule bone and contained within the temporal bone which is the most dense bone tissue in the entire human body). The same situation exists with respect to tissue materials which lead into the inner ear (e.g. the round window membrane). Exemplary inner ear tissue structures of primary importance for treatment purposes include but are not limited to the cochlea, the endolymphatic sac/duct, the vestibular labyrinth, and all of the compartments (and connecting tubes) which include these components. Access to the above-described inner ear tissue regions is typically achieved through a variety of structures, including but not limited to the round window membrane, the oval window/stapes footplate, the annular ligament, the otic capsule/temporal bone, and the endolymphatic sac/endolymphatic duct, all of which shall be considered middle-inner ear interface tissue structures as described in greater detail below. In addition, as indicated herein, the middle ear shall be defined as the physiological air-containing tissue zone behind the tympanic membrane (e.g. the ear drum) and ahead of the inner ear.
The inner ear tissues described above are of minimal size and only readily accessible through microsurgical procedures. In order to treat various diseases and conditions associated with inner ear tissues, the delivery of medicines to such structures is often of primary importance. Representative medicines which are typically used to treat inner ear tissues include but are not limited to urea, mannitol, sorbitol, glycerol, lidocaine, xylocaine, epinephrine, immunoglobulins, sodium chloride, steroids, heparin, hyaluronidase, aminoglycoside antibiotics (streptomycin/gentamycin), antioxidants, neurotrophins, nerve growth factors, various therapeutic peptides, and polysaccharides. Of particular interest in this list are compounds which are used to alter the permeability of the round window membrane within the ear. Likewise, treatment of inner ear tissues and/or fluid cavities may involve altering the pressure, volume, electrical activity, and temperature characteristics thereof. Specifically, a precise balance must be maintained with respect to the pressure of various fluids within the inner ear and its associated compartments. Imbalances in the pressure and volume levels of such fluids can cause various problems, including but not limited to conditions known as endolymphatic hydrops, endolymphatic hypertension, perilymphatic hypertension, perilymphatic hydrops, perilymphatic fistula, intracochlear fistula, Meniere's disease, and ruptures in various membrane structures within the ear.
Of further interest regarding the delivery of therapeutic agents to the middle ear, inner ear, and middle-inner ear interface tissues are a series of related and co-owned patents, namely, U.S. Pat. Nos. 5,421,818; 5,474,529, and 5,476,446 all to Arenberg. Each of these patents discloses a medical treatment apparatus designed to deliver fluid materials to internal ear structures. U.S. Pat. No. 5,421,818 describes a treatment system which includes a tubular stem attached to a reservoir portion with an internal cavity designed to retain a supply of therapeutic fluid compositions therein. The side wall of the reservoir portion further comprises fluid transfer means (e.g. pores or a semi-permeable membrane). Contact between the fluid transfer means and the round window membrane in a patient allows fluid materials to be delivered on-demand to the round window membrane, followed by diffusion of the fluid materials through the membrane into the inner ear. U.S. Pat. No. 5,474,529 involves a therapeutic treatment apparatus with a plurality of reservoir portions (e.g. a first and a second reservoir portion in a preferred embodiment) which are connected to multiple tubular stems that are designed for implantation into the endolymphatic sac and duct using standard surgical techniques. Finally, U.S. Pat. No. 5,476,446 discloses a therapeutic treatment apparatus which includes a reservoir portion for retaining liquid medicine materials therein, a first tubular stem on one side of the reservoir portion, and a second tubular stem on the opposite side of the reservoir portion. The second stem is designed to reside within the external auditory canal of a patient lateral to the ear drum, while the first stem is sized for placement within an opening formed in the stapes footplate/annular ligament so that medicine materials in fluid form can be delivered into the inner ear from the reservoir portion (which resides in the middle ear cavity medial to the ear drum).
Notwithstanding the systems described above, the present invention involves an improved medical treatment apparatus which provides many additional benefits. In accordance with the claimed invention, a unique and specially-designed treatment system is disclosed which is capable of performing a wide variety of basic functions including but not limited to (1) the repeatable and sustained active/passive delivery of therapeutic agents directly into the inner ear through the round window membrane; (2) the simultaneous measurement of inner ear electrical potentials (evoked or otherwise) using a technique known as "electrocochleography" (hereinafter "ECoG") which is discussed in greater detail below; (3) the controlled withdrawal, exchange, or replacement of inner ear fluid materials via the round window membrane; (4) the delivery of therapeutic fluid compositions to the round window membrane in a manner which is rapid, efficient, controllable, and uses a minimal number of steps and procedures; (5) the transfer of therapeutic fluid compositions to the round window membrane in a highly site-specific manner; (6) the removal of fluid materials from the round window membrane in a localized manner with minimal losses into adjacent tissue regions; (7) the ability to deliver and withdraw/exchange fluid materials from the inner ear at a precisely controlled rate which is readily undertaken using minimally-invasive surgical procedures; and (8) accomplishment of all the above-described goals using a system which is readily applicable to multiple patients having different sized ear structures Accordingly, the present invention represents an advance in the art of inner ear treatment, diagnosis, and medicine delivery as described in detail below